Combustion controlling device and method

ABSTRACT

A pseudo flame detecting portion detects a presence of a pseudo flame due to disturbance light when a sensor output of a flame sensor is equal to or greater than a pseudo flame threshold value and detects an absence of pseudo flame when the sensor output is equal to or less than another pseudo flame threshold value. The combustion controlling portion monitors the pseudo flame detection result from the pseudo flame detecting portion before an ignition attempt in the combustion equipment and, when the pseudo flame detection result continuously indicates presence of pseudo flame for a first monitoring time, cancels the ignition attempt in the combustion equipment.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to Japanese Patent Application No. 2017-052491, filed on Mar. 17, 2017, the entire contents of which are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a combustion controlling technique that controls a combustion depending on the presence or absence of a flame detected according to a sensor output of a flame sensor.

BACKGROUND ART

Combustion equipment used in industrial furnaces, boilers, air conditioners, kitchen appliances, heat exchangers, and the like is provided with a flame sensor that detects a light quantity of a flame in a burner and outputs an electrical signal, detects a presence or absence of a flame using a combustion controlling device based on the sensor output of this flame sensor, and controls a combustion based on the sensor according to the detection result.

Conventionally, such a combustion controlling device detects a presence or absence of a flame based on so-called hysteresis characteristics in which the extinction of a flame is detected at a flame extinction detection level lower than the ignition detection level that is the sensor output during detection of ignition in order to suppress effects of output changes of a flame sensor due to fluctuations of a flame (see, for example, PTL 1 and the like).

CITATION LIST Patent Literature

[PTL 1] JP-B-7-15328

[PTL 2] Japanese Patent No. 3943478

SUMMARY

However, since the presence or an absence of a flame is detected by comparing the sensor output of the flame sensor with a threshold value in the related art described above, in an environment in which there is a pseudo flame having a light quantity equal to or higher than the flame extinction detection level and equal to or lower than the ignition detection level due to effects of disturbance light, such as outside light or stray light, even if a flame is extinguished after ignition, the sensor output of the flame sensor may not be reduced to the flame extinction detection level. Since the flame extinction cannot be detected in such a case, fuel continues to be output after extinction and a very dangerous state may be entered.

There is a proposed technique for preventing disturbance light from entering the flame sensor by improving the burner structure to suppress effects of such disturbances (see, for example, PTL 2 or the like). However, since the measure against the problem depends on the equipment manufacturer, not all combustion devices surely take the measure described above. In addition, application of the burner structure described above significantly increases the cost for measures since a change to existing combustion equipment, such as an exchange of an existing burner, is necessary.

The invention addresses such a problem with an object of providing a combustion controlling technique capable of controlling combustion equipment safely with respect to disturbance light without changing existing combustion equipment.

To achieve the object described above, according to the invention, there is provided a combustion controlling device that controls a combustion in combustion equipment based on a presence or an absence of a combustion flame in the combustion equipment detected from a sensor output of a flame sensor, the combustion controlling device comprising a combustion flame detecting portion that detects a presence or an absence of a combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during combustion in the combustion equipment and a preset combustion flame threshold value; a pseudo flame detecting portion that detects a presence or an absence of a pseudo flame based on the sensor output and a preset pseudo flame threshold value less than the combustion flame threshold value; and a combustion controlling portion that controls a combustion in the combustion equipment based on a combustion flame detection result obtained by the combustion flame detecting portion, in which the combustion controlling portion monitors a pseudo flame detection result by the pseudo flame detecting portion before an ignition attempt in the combustion equipment and, when the pseudo flame detection result continuously indicates presence of a pseudo flame for a first monitoring time, cancels the ignition attempt in the combustion equipment.

In addition, in one example of the configuration of the combustion controlling device according to the invention, the combustion flame threshold value includes a first combustion flame threshold value and a second combustion flame threshold value less than the first combustion flame threshold value and the combustion flame detecting portion detects a presence of a combustion flame in the combustion equipment when the sensor output of the flame sensor is equal to or greater than the first combustion flame threshold value and detects an absence of a combustion flame when the sensor output is equal to or less than the second combustion flame threshold value.

In addition, in one example of the configuration of the combustion controlling device according to the invention, the pseudo flame threshold value includes a first pseudo flame threshold value and a second pseudo flame threshold value less than the first pseudo flame threshold value and the pseudo flame detecting portion detects a presence of a pseudo flame due to disturbance light when the sensor output of the flame sensor is equal to or greater than the first pseudo flame threshold value and detects an absence of a pseudo flame when the sensor output is equal to or less than the second pseudo flame threshold value.

In addition, in one example of the configuration of the combustion controlling device according to the invention, the combustion controlling portion starts the ignition attempt in the combustion equipment when the pseudo flame detection result continuously indicates an absence of a pseudo flame for a second monitoring time before the ignition attempt.

In addition, according to the invention, there is provided a combustion control method that controls a combustion in combustion equipment based on a presence or an absence of a combustion flame in the combustion equipment detected from a sensor output of a flame sensor, the method comprising a combustion flame detecting step in which a combustion flame detecting portion detects a presence or an absence of a combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during combustion in the combustion equipment and a preset combustion flame threshold value; a pseudo flame detecting step in which a pseudo flame detecting portion detects a presence or an absence of a pseudo flame based on the sensor output and a preset pseudo flame threshold value less than the combustion flame threshold value; and a combustion controlling step in which a combustion controlling portion controls a combustion in the combustion equipment based on a combustion flame detection result obtained in the combustion flame detecting step, in which the combustion controlling step monitors a pseudo flame detection result in the pseudo flame detecting step before an ignition attempt in the combustion equipment and, when the pseudo flame detection result continuously indicates a presence of a pseudo flame for a first monitoring time, cancels the ignition attempt in the combustion equipment.

According to the invention, when the pseudo flame detection result from the pseudo flame detecting portion continues for the first monitoring time even though combustion in the burner does not start before an ignition attempt, since such disturbance light is detected constantly and combustion flame may not be detected accurately if combustion in the burner is started, the ignition attempt in the combustion equipment is canceled. Accordingly, the combustion equipment can be controlled safely with respect to disturbance light. In addition, since a presence or an absence of a pseudo flame due to disturbance light is detected by the combustion controlling device, the structure of the burner does not need to be changed to prevent disturbance light from entering the flame sensor. With this, it becomes unnecessary to perform a change to existing combustion equipment, such as an exchange of an existing burner, so a significant increase in the cost for measures can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the structure of the combustion controlling device.

FIG. 2 is an explanatory diagram illustrating a combustion flame detection operation.

FIG. 3 is an explanatory diagram illustrating a pseudo flame detection operation.

FIG. 4 is a flowchart illustrating an ignition attempt execution decision process.

DETAILED DESCRIPTION

Next, an embodiment of the invention will be described with reference to the drawings.

Combustion Controlling Device

First, a combustion controlling device 10 according to the embodiment will be described with reference to FIG. 1. FIG. 1 is a block diagram illustrating the structure of the combustion controlling device.

This combustion controlling device 10 performs combustion control of combustion equipment 30 based on a sensor output S from a flame sensor 20.

The combustion equipment 30 may be general combustion equipment used in industrial furnaces, boilers, air conditioners, kitchen appliances, heat exchangers, and the like and has the function of generating thermal energy by burning fuel in a burner.

The flame sensor 20 detects the light quantity of flame in the burner of the combustion equipment 30, converts the light quantity to electricity, and outputs the electricity to the combustion controlling device 10 as the sensor output S.

The combustion controlling device 10 is provided with a combustion flame detecting portion 11, a pseudo flame detecting portion 12, and a combustion controlling portion 13 as main function portions. Each of these function portions may be configured as a controlling circuit comprising ICs or may be achieved in cooperation between a CPU and programs.

The combustion flame detecting portion 11 has the function of detecting a presence or an absence of a combustion flame in the combustion equipment 30 based on the sensor output S of the flame sensor 20 and a preset combustion flame threshold value. When hysteresis characteristics are applied to the detection of combustion flame, a first combustion flame threshold value H1 (ignition detection level) and a second combustion flame threshold value H2 (flame extinction detection level) that is less than the first combustion flame threshold value H1 are used as combustion flame threshold values.

FIG. 2 is an explanatory diagram illustrating a combustion flame detection operation. The combustion flame detecting portion 11 detects a presence (Bon) of a combustion flame in the combustion equipment 30 when the sensor output S of the flame sensor 20 is equal to or greater than the first combustion flame threshold value H1 (ignition detection level) and detects an absence (Boff) of a combustion flame when the sensor output S is equal to or less than the second combustion flame threshold value H2 (flame extinction detection level) less than the first combustion flame threshold value H1.

The pseudo flame detecting portion 12 has the function of detecting a presence or an absence of a pseudo flame due to disturbance light based on the sensor output S of the flame sensor 20 and a preset pseudo flame threshold value. A pseudo flame is not a combustion flame that indicates actual combustion in the combustion equipment 30, but is a quasi-flame in which the level of the sensor output S is raised by effects of disturbance light, such as outside light or stray light. When hysteresis characteristics are applied to the detection of a pseudo flame, a first pseudo flame threshold value H3 (pseudo flame presence detection level) and a second pseudo flame threshold value H4 (pseudo flame absence detection level) less than the first pseudo flame threshold value H3 are used as pseudo flame threshold values.

FIG. 3 is an explanatory diagram illustrating a pseudo flame detection operation. The pseudo flame detecting portion 12 detects a presence (Pon) of a pseudo flame due to disturbance light when the sensor output S of the flame sensor 20 is equal to or greater than the pseudo flame threshold value H3 (pseudo flame presence detection level) and detects an absence (Poff) of a pseudo flame when the sensor output S is equal to or less than the pseudo flame threshold value H4 (pseudo flame absence detection level). At this time, a presence or an absence of a pseudo flame can be detected more strictly by making the pseudo flame threshold values H3 and H4 less than the second combustion flame threshold value H2. It should be noted that the pseudo flame threshold values H3 and H4 may be changed adaptively. In addition, although stable detection can be achieved by applying hysteresis characteristics to the detection of a pseudo flame, hysteresis characteristics are not necessary for the invention and pseudo flame threshold values H3 and H4 only need to be set to the same value when hysteresis characteristics are not applied.

The combustion controlling portion 13 has the function of controlling combustion in the combustion equipment 30 based on a combustion flame detection result B from the combustion flame detecting portion 11 during combustion in the combustion equipment 30. The combustion control performed here is the same as the conventional one. For example, when the combustion flame detection result B indicates a presence (Bon) of a combustion flame, a control signal C for instructing the supply of fuel to the burner is output to the combustion equipment 30. When the combustion flame detection result B indicates an absence (Boff) of a combustion flame, a control signal C for instructing the stopping of the supply of fuel to the burner is output to the combustion equipment 30.

In addition, the combustion controlling portion 13 monitors a pseudo flame detection result P from the pseudo flame detecting portion 12 before an ignition attempt in the combustion equipment 30, cancels the ignition attempt in the combustion equipment 30 when the pseudo flame detection result P continuously indicates a presence of a pseudo flame for a preset first monitoring time T1, and starts an ignition attempt in the combustion equipment 30 when the pseudo flame detection result P continuously indicates an absence of a pseudo flame for a preset second monitoring time before the ignition attempt.

When the pseudo flame detection result P indicates a presence of a pseudo flame, the operation of the combustion equipment 30 may be completely stopped by making a lockout of the combustion equipment 30 continuously for a certain time. In addition, when the pseudo flame detection result P indicates a presence of a pseudo flame, a lockout may be made immediately or a lockout may not be made after a certain period of waiting is performed.

Operation of the Embodiment

Next, the operation of the combustion controlling device 10 according to the embodiment will be described with reference to FIG. 4. FIG. 4 is a flowchart illustrating an ignition attempt execution decision process.

The combustion controlling portion 13 makes the ignition attempt execution decision process illustrated in FIG. 4 before starting an ignition attempt in the combustion equipment 30.

First, the combustion controlling portion 13 obtains the pseudo flame detection result P from the pseudo flame detecting portion 12 (step 100). When the sensor output S of the flame sensor 20 is equal to or less than the pseudo flame threshold value H4 and the pseudo flame detection result P indicates an absence (Poff) of a pseudo flame (NO in step 101), the combustion controlling portion 13 starts an ignition attempt in the combustion equipment 30 (step 102) and ends a series of the ignition attempt execution decision processes. After that, the combustion controlling portion 13 starts the combustion control of the combustion equipment 30 based on the combustion flame detection result B from the combustion flame detecting portion 11.

In contrast, when the sensor output S of the flame sensor 20 is equal to or greater than the pseudo flame threshold value H3 and the pseudo flame detection result P indicates a presence (Pon) of a pseudo flame (YES in step 101), the combustion controlling portion 13 starts monitoring the pseudo flame detection result P after that (step 103).

When the sensor output S of the flame sensor 20 is kept at the pseudo flame threshold value H3, or greater, and the pseudo flame detection result P continuously indicates a presence (Pon) of a pseudo flame for the first monitoring time (YES in step 104), since disturbance light is detected constantly by the flame sensor 20 and combustion flame may not be detected accurately, the combustion controlling portion 13 cancels the ignition attempt in the combustion equipment 30 (step 105) and ends a series of the ignition attempt execution decision processes. At this time, the combustion controlling portion 13 may stop the operation of the combustion equipment 30 (that is, a lockout) as a specific example of canceling the ignition attempt. This can provide a high level of safety.

In addition, when the pseudo flame detection result P does not continuously indicate a presence (Pon) of a pseudo flame for the first monitoring time (NO in step 104) and the pseudo flame detection result P continuously indicates an absence (Poff) of a pseudo flame for the second monitoring time (YES in step 106), since the flame sensor 20 can detect combustion flame accurately because it does not detect disturbance light, the processing proceeds to step 102 and the combustion controlling portion 13 starts an ignition attempt in the combustion equipment 30.

Alternatively, when a presence (Pon) of a pseudo flame does not continue for the first monitoring time and an absence (Poff) of a pseudo flame does not continue for the second monitoring time (NO in step 106), the processing returns to step 103 and the combustion controlling portion 13 continues the monitoring of the pseudo flame detection result P.

The first monitoring time and the second monitoring time only need to be preset depending on the combustion equipment 30 that is a control target and the first monitoring time and the second monitoring time may be set to the same value.

Effects of the Embodiment

As described above, in the embodiment, the pseudo flame detecting portion 12 detects a presence (Pon) of a pseudo flame due to disturbance light when the sensor output S of the flame sensor 20 is equal to or greater than the pseudo flame threshold value H3 and detects an absence (Poff) of a pseudo flame when the sensor output S is equal to or less than the pseudo flame threshold value H4. The combustion controlling portion 13 monitors the pseudo flame detection result P from the pseudo flame detecting portion 12 before an ignition attempt in the combustion equipment 30 and cancels the ignition attempt in the combustion equipment 30 when the pseudo flame detection result P continuously indicates a presence of a pseudo flame for the first monitoring time.

Accordingly, when the pseudo flame detection result P from the pseudo flame detecting portion 12 continues for the first monitoring time even though combustion in the burner does not start before an ignition attempt, since such disturbance light is detected constantly and combustion flame may not be detected accurately if combustion in the burner is started, the ignition attempt in the combustion equipment 30 is canceled. Accordingly, the combustion equipment 30 can be controlled safely with respect to disturbance light. In addition, since a presence or an absence of a pseudo flame due to disturbance light is detected by the combustion controlling device 10, the structure of the burner does not need to be changed to prevent disturbance light from entering the flame sensor 20. With this, it becomes unnecessary to perform a change to the existing combustion equipment 30, such as an exchange of an existing burner, so a significant increase in the cost for measures can be suppressed.

Extension of the Embodiment

Although the invention has been described above with reference to the embodiment, the invention is not limited to the above embodiment. Various changes understandable to those skilled in the art can be made to the structure and details of the invention within the scope of the invention.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

10: combustion controlling device; 11: combustion flame detecting portion; 12: pseudo flame detecting portion; 13: combustion controlling portion; 20: flame sensor; 30: combustion equipment; S: sensor output; H1: first combustion flame threshold value; H2: second combustion flame threshold value; H3: first pseudo flame threshold value; H4: second pseudo flame threshold value; B: combustion flame detection result; P: pseudo flame detection result: C: control signal 

1. A combustion controlling device that controls a combustion in combustion equipment based on a presence or an absence of a combustion flame in the combustion equipment detected from a sensor output of a flame sensor, the combustion controlling device comprising: a combustion flame detecting portion that detects the presence or the absence of the combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during the combustion in the combustion equipment and a preset combustion flame threshold value; a pseudo flame detecting portion that detects a presence or an absence of a pseudo flame based on the sensor output and a preset pseudo flame threshold value less than the combustion flame threshold value; and a combustion controlling portion that controls the combustion in the combustion equipment based on a combustion flame detection result obtained by the combustion flame detecting portion, wherein the combustion controlling portion monitors a pseudo flame detection result by the pseudo flame detecting portion before an ignition attempt in the combustion equipment and, when the pseudo flame detection result continuously indicates the presence of the pseudo flame for a first monitoring time, cancels the ignition attempt in the combustion equipment.
 2. The combustion controlling device according to claim 1, wherein the combustion flame threshold value includes a first combustion flame threshold value and a second combustion flame threshold value less than the first combustion flame threshold value, and the combustion flame detecting portion detects the presence of the combustion flame in the combustion equipment when the sensor output of the flame sensor is equal to or greater than the first combustion flame threshold value and detects the absence of the combustion flame when the sensor output is equal to or less than the second combustion flame threshold value.
 3. The combustion controlling device according to claim 2, wherein the pseudo flame threshold value includes a first pseudo flame threshold value and a second pseudo flame threshold value less than the first pseudo flame threshold value, and the pseudo flame detecting portion detects the presence of the pseudo flame due to disturbance light when the sensor output of the flame sensor is equal to or greater than the first pseudo flame threshold value and detects the absence of the pseudo flame when the sensor output is equal to or less than the second pseudo flame threshold value.
 4. The combustion controlling device according to claim 3, wherein the combustion controlling portion starts the ignition attempt in the combustion equipment when the pseudo flame detection result continuously indicates the absence of the pseudo flame for a second monitoring time before the ignition attempt.
 5. The combustion controlling device according to claim 2, wherein the combustion controlling portion starts the ignition attempt in the combustion equipment when the pseudo flame detection result continuously indicates the absence of the pseudo flame for a second monitoring time before the ignition attempt.
 6. The combustion controlling device according to claim 1, wherein the pseudo flame threshold value includes a first pseudo flame threshold value and a second pseudo flame threshold value less than the first pseudo flame threshold value, and the pseudo flame detecting portion detects the presence of the pseudo flame due to disturbance light when the sensor output of the flame sensor is equal to or greater than the first pseudo flame threshold value and detects the absence of the pseudo flame when the sensor output is equal to or less than the second pseudo flame threshold value.
 7. The combustion controlling device according to claim 1, wherein the combustion controlling portion starts the ignition attempt in the combustion equipment when the pseudo flame detection result continuously indicates the absence of the pseudo flame for a second monitoring time before the ignition attempt.
 8. A combustion control method that controls a combustion in combustion equipment based on a presence or an absence of a combustion flame in the combustion equipment detected from a sensor output of a flame sensor, the method comprising: detecting, by a combustion flame detecting portion, the presence or the absence of the combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during the combustion in the combustion equipment and a preset combustion flame threshold value; detecting, by a pseudo flame detecting portion, a presence or an absence of a pseudo flame based on the sensor output and a preset pseudo flame threshold value less than the combustion flame threshold value; and controlling, by a combustion controlling portion, the combustion in the combustion equipment based on a combustion flame detection result obtained in the combustion flame detecting, wherein the combustion controlling comprises monitoring a pseudo flame detection result in the pseudo flame detecting before an ignition attempt in the combustion equipment and, when the pseudo flame detection result continuously indicates the presence of the pseudo flame for a first monitoring time, canceling the ignition attempt in the combustion equipment. 